Three species of egg parasites, viz.,Anagrus sp.,A. optabilis (Mymaridae) andOligosita sp. (Trichogrammatidae), and a nymphal/adult parasiteGonatopus sp. of rice planthoppers were studied for their biology and control potential. Larger number of adult mymarids emerged from host eggs between 8·30 a.m. and 12·30 p.m. of the day whereas trichogrammatid adults emerged between 12·30 p.m. to 4·30 p.m. All the three species parasitised both brown planthopper (BPH) and white backed planthopper (WBPH) but, in general, failed to parasitise rice leaf-hoppers.
Developmental duration from oviposit ion to adult emergence noted for these parasites indicated that males of mymarids, in general, developed faster (10–11 days) than females (12–13 days) at 20–32° C prevailing during October, whereasOligosita females developed more slowly (14–15 days). However, bothA. optabilis andOligosita developed three days faster at 30–38° C prevailing during April, Fecundity in terms of number of eggs parasitised per female varied from 12·3 to 20·3. Under greenhouse conditions, release of 1 and 5 pairs of mymarid parasites for 10 days reduced the nymphal hatch of BPH by 60 and 85%, respectively. Nymphal/adult parasiteGonatopus sp. completed its life cycle in 19·5 to 31 days on both BPH and WBPH. While the 4th and 5th instar nymphs of BPH were parasitised more frequently, green leafhopper nymphs were not parasitised. Besides being endoparasitic, the adult females also predated on and killed as many as 5·2 nymphs a day.